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Unions representing steelworkers and letter carriers are signing on to a new group

Quarterly filings are due with the Federal Election Commission on Saturday

Washington (CNN)Seven labor groups have joined forces with a Democratic super PAC trying to pool their party's field programs, an effort that the group claims has now raised $60 million.

For Our Future, a new outside group set on avoiding duplication among traditional powerplayers on the left, will report this weekend having collected millions from a new corps of donors, including unions representing steelworkers and letter carriers, the group told CNN Friday. Yet the biggest supporter remains Tom Steyer, the billionaire climate activist who was the Democratic Party's top donor during the 2014 cycle.

Steyer has given $20 million to the organization through his personalized super PAC, NextGen Climate, and said in an interview Thursday that he did not plan to increase the size of that commitment in the coming weeks. Other top givers to the super PAC are Dustin Moskovitz, the Facebook co-founder who has stunned Democrats by injecting groups with $35 million out of nowhere, and his wife who together donated $5 million to For Our Future.

"The organization is basically in place," Steyer said. "If we decided at this point, 'Let's go do Hawaii', you really can't."

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Democrats have long struggled to coordinate their field program, and the numbers reveal some success at least at generating buy-in to the effort. But nearly half of the super PAC's money, including $15 million of Steyer's, remained purely as commitments as of September 30, when the third fundraising quarter ended -- the super PAC will only report $29 million in contributions in the door.

"We are really proud of the cross section of labor, progressive groups and individuals who have invested in this critical ground game operation to win on November 8," said Amanda Brown, the head of For Our Future, "and to continue the conversations in our communities after the election to advocate for the issues these voters care about."

The unions that joined the effort earlier have given more substantial amounts: AFSCME contributed $4.8 million; the American Federation of Teachers donated $4.1 million; the AFL-CIO gave $2.3 million; and the National Education Association handed over another $2.1 million.

But in August and September, the super PAC quietly recruited a new set of partners, their financial report will show: the Communications Workers of America, the National Association of Letter Carriers, United Steelworkers, United Automobile Workers and the American Federation of Government Employees, each of which forked over $1 million to join the collective.

Other new members are the Office of Professional Employees International Union, Unite HERE and the trial-lawyers group, American Association of Justice, each of which gave smaller amounts.

The nearly dozen unions have pledged another $15 million, according to the group. Quarterly filings are due with the Federal Election Commission Saturday.